I am refurbishing a San Juan 26 and am at the point of replacing the old rotted bulkheads. Got the big one on the port side out and used it to cut out a new one out of marine ply. The old one was attached to the hull liner with about ten screws and it came out easy. I have seen sites where the bulkheads were fiberglassed in place and was thinking about installing the new ones with fillets and glass tape at the perimeter. Is there any downside to glassing them in place?

No downside at all. When tabbing the bulkhead, use epoxy and roving, not fiberglass cloth. wet the hull and bulkhead with a brished on amount of epoxy, then apply saturated roving. Use a matt roller and squeegee to make sure that there is good contact with the hull & bulkhead. Mask off any area that you don't epoxy on including the floor. Use gloves.

You can see where the old tabbing was in the first set of photos in the following link. In our configuration, the bulkhead is screwed in place to hold it while the tabbing is curing.

But the bulkhead should not touch the hull. If it does it creates a hard spot. The solution is to get some foam, closed cell, and glue it to the hull and reduce the bulkhead's dimensions by the same amount. Any cheap foam is fine as it is only a spacer. It has to be closed cell though so it doesn't suck epoxy from the tabbing. The foam can be cut in such a shape that it provides a bevel to the hull edge that will make glassing easier. When it's all done the tabbing will support the bulkhead evenly as it should. It will go a long way towards stiffening the hull over the original screw fastened bulkheads.

mitiempo is correct. I left about 1/2 inch of space between the bulkhead and hull. No foam, but I like the idea. I just reproduced what Sabre had done. It's not that hard a job - about 20 hours on our port side and less than 10 on the starboard.

No downside at all. When tabbing the bulkhead, use epoxy and roving, not fiberglass cloth. wet the hull and bulkhead with a brished on amount of epoxy, then apply saturated roving. Use a matt roller and squeegee to make sure that there is good contact with the hull & bulkhead. Mask off any area that you don't epoxy on including the floor. Use gloves.

You can see where the old tabbing was in the first set of photos in the following link. In our configuration, the bulkhead is screwed in place to hold it while the tabbing is curing.

If making a similar repair, should we have any structural concerns about the bolts on the chainplate being attached to a new insert instead of being attached to a larger single replacement bulkhead? I see in your photos Sabreman that you've still got three bolts attached to the original bulkhead which probably suffices (although the third from the bottom doesn't have much wood from the original bulkhead above it), but wouldn't the high forces on the chainplate tend to pull the insert away from the original bulkhead and up into the deck? Maybe the deck is expected to provide the necessary counter-acting force and this is OK, or in general, would it be better to replace the whole bulkhead? (Sorry, not a criticism of your project Sabreman - nice job; I'm just hoping to understand the issues/pros/cons of various approaches).

Good questions and ones that I considered for this repair. No offense taken. When I repaired the port side bulkhead, I replaced the entire bulkhead in a traditional manner as shown in the following link.

For the starboard side, the rotted area was small (6" square) so I elected to insert a panel and tie the repair to the old and new sections as a way of distributing the load. It was a calculated decision since the shrouds to which the chainplate is attached are the forward lowers and under far less load than the uppers. The fact that I'd have to disassemble 2 cabinets, an A/C unit, and shelving also played into the decision.

I cut well into good wood. The replacement panel is scrafed with a rabbit. I would have liked a taper but it was not possible since I was working in a closet. The panel is joined to the existing bulkhead with thickened epoxy and a layer of fiberglass cloth which is only there for lateral stability.

You are correct that the deck provides counter resistance but I didn't count on it since the panel extends outward nearly to the hull (1/2" gap) and is tabbed to the hull and well down into the existing bulkhead. For tabbing, I used roving and not cloth. When I tensioned the shroud, I watched for any distortion. If I saw any, I was prepared to replace the entire bulkhead. Not only was there no distortion, it didn't even creak. After a full season in wind up to 20 kts, there is no distortion or slackening of the shroud. I'm confident of the repair but if I detect any compromise, then the whole thing will come out..... it's not like I haven't done this before! It's only time and virtually no money.

I would like to have had access to the biaxial cloth. Roving tends to fall apart while being cut to size. I had to be really careful not to displace the fibers while cutting, wetting, and applying it. Unfortunately WM didn't have any and I was on a timeline.....

I think that my repairs are strong enough and roving is what Sabre used, but if I had my choice.......

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